The research proposed for this project is intended to augment our fundamental understanding of[unreadable] arsenic (As) behavior in ways that lead directly to a reduction in human exposure in both the U.S. and in[unreadable] Bangladesh. At the Vineland Chemical Superfund site in New Jersey, heavily contaminated with both[unreadable] inorganic As (InAs) and organic As (OrgAs), research will focus on reducing off-site transport of these[unreadable] contaminants in two ways. The effort will first be directed at polishing effluent from the existing treatment[unreadable] plant using a treatment column containing zero-valent iron (Fe(0)) filings which, this project's previous[unreadable] research has demonstrated, is capable of removing both InAs and OrgAs. Second, the feasibility of reducing[unreadable] off-site transport of As will be explored by installing and monitoring a permeable-reactive barrier containing[unreadable] Fe(0) filings.[unreadable] In Bangladesh, we are ethically compelled to lower the As exposure of study participants in Projects[unreadable] 2, 3, and 4. The proposed research will focus on the sustainability of continued withdrawals from those[unreadable] aquifers that are currently low in As. The justification is that these aquifers are currently the only realistic[unreadable] alternative for the approximately 50 million inhabitants of the country who have been drinking well water with an As[unreadable] content that often exceeds the WHO guideline of 10 ug/L by one to two orders of magnitude. Through[unreadable] detailed monitoring and targeted manipulations in the field and in the laboratory, the combination of[unreadable] hydrological, geochemical, and microbial processes that maintain As concentrations at low levels in both[unreadable] very shallow (<10 m) and deep (>30-150 m) aquifers will be investigated. In a direct application of the[unreadable] approach to mitigation developed under the previous round of funding, the exposure to As and Mn of[unreadable] children and adults, participating in Project 3 and 4 and residing in 25 villages, will be rapidly reduced by[unreadable] targeting safe aquifers for the installation of community wells. The timing of these interventions will be[unreadable] closely synchronized with parallel studies of their health impact, conducted under biomedical components of[unreadable] this application.